Method and device for moisturizing a web,including an air header with perforated walls

ABSTRACT

A SYSTEM FOR UNIFORMLY DISPERSING A LIQUID MEDIUM SUCH AS WATER, TO A WEB. THE WEB IS CONTINUALLY CONVEYED BETWEEN A HEADER AND A SUCTION BOX. WITHIN THE HEADER, TWO GASES AT DIFFERENT STATES AND CONTAINING DIFFERENT RELATIVE AMOUNTS OF THE MEDIUM ARE MIXED TO PRODUCE A MIST. THIS MIST IS THEN CARRIED INTO AND THROUGH THE WEB BY THE ACTION OF THE SUCTION BOX.

W- 1974 v J. c. URBAS 3,838,000

IETHOD AND DEVICE FOR "OISTURIZING A. WEB, INCLUDING A" 'AIR. HEADERWITH PERFORATED WALLS F11 5 Junei, 1972 2 Sheets-Sheet 1 United StatesEatent O 3,838,000 METHOD AND DEVICE FOR MOISTURIZING A WEB, INCLUDINGAN AIR HEADER WITH PERFORATED WALLS John 'C. Urbas, Dorval, Quebec,Canada, assignor to Midland-Ross Corporation, Cleveland, Ohio Filed June5, 1972, Ser. No. 259,794 Claims priority, application Canada, May 5,1972,

141,416 Int. Cl. D21f 7/00 US. Cl. 162-207 4 Claims ABSTRACT OF THEDISCLOSURE A system for uniformly dispersing a liquid medium, such aswater, to a web. The web is continually conveyed between a header and asuction box. Within the header, two gases at different states andcontaining different relative amounts of the medium are mixed to producea mist. This mist is then carried into and through the web by the actionof the suction box.

BACKGROUND OF THE INVENTION In the adding of a medium, such as water, toa continuously moving web, it is desirable to add the medium in auniform manner. lPrior methods for adding such a medium to a web werespraying, condensing, and use of medium rolls, but these prior methodshad fundamental shortcomings, such as, nonuniformity of the application,limited moisture addition, dripping, lack of controlled application, andinterference with production efiiciency. One method of moisturizing aweb is described by S. W. Speers in U.S. Pat. 3,320,676. -In his method,Speers subjects a web to a mist directed to both sides of the websurface by a plurality of nozzles. The web is then conveyed through ahumidity chamber for the purpose of having the moisture soak through theweb. After the web leaves the humidity chamber, another set of nozzlessprays mists on the surfaces of the web once more. Although Speersmethod is an advancement over the then prior methods of adding moistureto a web, the uniformity can be improved upon, and a simpler apparatusis desirable.

OBJECTS OF THE INVENTION It is therefore an object of this invention toprovide means and methods of adding liquid to a web with uniformityhereunto unavailable.

It is another object of this invention to provide means for uniformlymoisturizing a continuously moving paper web.

It is still another object of this invention to add mois ture to a webwithout encountering a dripping problem.

It is a further object of this invention to provide means for adding aliquid medium to a continuously moving web in a controlled manner.

It is still a further object of this invention to provide means andmethods for moisturizing a paper web in an economical and simple manner.

It is another object of this invention to provide relatively simple andinexpensive means for adding a liquid medium in a uniform and controlledmanner to a moving web.

These and other objects and features of the invention will become moreapparent from the following description and accompanying drawing,wherein:

FIG. 1 is a schematic view illustrating web treating equipment whichincorporates the principles of this invention:

FIG. 2 is a detailed cross-sectional view illustrating the means formoisturizing a continuously moving paper web; and

FIG. 3 is a diagram illustrating an example of results achieved when twobodies of air having different conditions are mixed.

SUMMARY OF THE INVENTION The invention utilizes the mixing of two ormore gas streams having different states with the intent of producing amist of the medium. Throughout the description the invention will bedescribed by the use of adding moisture to an air-permeable paper web;however, it will be understood that this is for purposes of illustrationonly and it is not intended to be limited thereto as other condensableliquids may be added to various webs utilizing the principles expressedherein. Two or more streams of air having different temperatures andrelative humidities are mixed with one another within a chamber that isspaced relative to a suction box. As a result of this mixing, a mist ofwater vapor is formed. The air-permeable web is conveyed between thechamber and the suction box and this mist is drawn therethrough by theaction of the suction box on the surface of the web opposite thehumidity chamber. It has been found that in this way a controlleduniform amount of moisture may be added to a paper web.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, apaper web treating apparatus is shown having a steam dryer roll 10 and asweat dryer roll 12. Disposed intermediate these two dryer rolls 10, 12is a felt roll 14 about which a felt 16 travels that is subsequentlyconveyed about the sweat roll 12. There is a second felt roll 18 on theopposite side of the sweat roll to receive the felt 16. The felt 16 isa. foraminous material of the general type used for support during thetreating of a paper web. There are a plurality of other felt rolls 20,22, 24 and 26 which, in cooperation with the other rolls 12, 14 and 18,convey the felt as shown in the drawing. Adjacent the felt conveyingportion of the apparatus are a plurality of calender rolls 28 in tandemwhich calender an uncalendered paper Web 30 which has been previouslyconveyed about the steam dryer 10, the sweat dryer 12 and eventuallyalong a horizontal and upwardly extending web path to the top nip 29between the top two calender rolls 28.

Intermediate the felt rolls 18 and 20 is a humidifier 32 which comprisesa hollow suction box 34 and an air header 36 located on the upper andlower sides, respectively, of the web path. The air header 36 isrectangular and has side walls 38, a floor 39 and an outer top wall 40,having a multiplicity of small openings 42 therein and facing thesuction box as shown. Positioned within the air header 36 intermediatethe floor 39 and the top wall 40 is an interior perforated wall 44 whichextends to each of the side walls 38 and defines a pair of chamber 46and 47 in the lower and upper portions of the air header, respectively.One wall 38 of the header 36 has an opening 48 confluent with thechamber 46 and receives a pipe 50 therein. Located within the upperchamber 47 are a plurality of ported tubes 52. The suction box 34 isrectangular in configuration and is made up of a series of walls 54there being a flat perforated wall 56 positioned in opposed generallyparallel relation with the perforated wall 40 of the air header 36. Oneof the walls 54 has an opening 58 which receives a pipe 60, which pipeis in communication with a pump 62 that creates a partial vacuum withinthe box 34, thereby drawing air under pressure through the perforationsof wall 56 and causing the air within the air header 36 to be drawnthrough the openings 42 and toward the suction box 34.

For mixing the two streams of saturated air to the extent required inachieving stated objects of the invention, i.e., uniformly adding aliquid to a web to uniform ly moisturize it, the perforated walls 40, 44and 56, and tubes 52 of the header 36 are preferably constructed andarranged in a generally coextensive relationship along the web path asshown in FIG. 2. The perforated areas of the walls 40, 44 and 56 areshown as substantially coextensive in the widewise direction of thesewalls, i.e., the direction of web travel, as indicated by perforationscorresponding to the arrows. The tubes 52 are shown generally uniform-1y spaced in the same widewise direction within the chamber 47 to effectgeneral distribution of air discharged from the tubes 52 throughout thechamber 47 and uniform mixing with the saturated air of differenttemperature entering chamber 47 from chamber 46 through the apertures ofwall 44. Obviously, the wall 40 apertured as shown restricts the freeescape of air therefrom and thus promotes effective mixing of the twostreams within the chamber 47 before they pass in mixed and mistycondition through the apertures of wall 40. As the opposing aperturedareas of walls 40 and 56 are shown substantially coextensive, operationof the suction box 34 assures that the partial vacuum conditionsadjacent the apertured wall 56 thereof causes the passage of misty airefiiuent from apertures 42 of wall 40 into and through the web 30.

In operation, the felt 16 is conveyed about the rolls 14, 18, 20, 22, 24and 26 as shown in FIG. 1. The paper web 30 is carried about the steamdryer roll where it is partially dried. The web 30 then is conveyedintermediate the sweat dryer 12 and felt 16 where it is further dried.After rotating about the roll 12, the web 30 and felt 16 are conveyedalong a relatively straight path between rolls 18 and 20. The web 30 andfelt 16 pass through the humidifier 32 intermediate the suction box 34and the air header 36. Downstream from the humidifier 32 the felt 16parts from the web 30 by rotating about roll 20 toward roll 22 and theweb passes through the first nip 29 of the calender rolls 28 andsubsequently leaves the calender rolls through the bottom nip 31.Alternatively, the web 30 may be diverted, as shown by the dotted arrow,so that it does not pass through the humidifier, but instead is conveyeddirectly to roll 24.

As the felt 16 and web pass between the suction box 34 and the airheader 36, the suction created within the box 34 pulls the felt 16 andweb 30 towards the perforated plate 56. Within the air header 36relatively warm humid air is conveyed through pipe 50 into the lowerchamber 46 and escapes through the multiplicity of small openings shownwithin plate 44 to enter the upper chamber 47. Relatively cool moist airis delivered into the upper chamber 47 through the ported tubes 52.

The two streams of air mix within the chamber 47 and through selectionof the proper characteristics or conditions of these two gases, a mistis formed. This mist is then pulled through the openings 42 in theperforated plate 40, because of the action of the suction box 34,through the paper web 30 and felt 16.

The individual temperatures, relative humidities and action of the airstreams may be varied to control the supply of moisture to the web 30.The system employs controlled precipitation of moisture by adding twopsy chrometrically prepared air streams to effect precise avail abilityof water mist in the air. As an example of the air streams that may beused, FIG. 3 shows two air streams of sufficiently different humidity togenerate a mist. Three mixing lines are shown where 70 F. saturated airis mixed with 174, 165 and 160 saturated air. The saturated conditionsare merely used as examples and, in actual practice, unsaturated airshould be used to minimize dripping on the header surfaces prior tomixing. The mixing line may be used to forecast the concentration offree water, or fog, in the air and may be replotted similar to the curveshown in FIG. 3. Where equal proportions of warm and cool air are mixed,e.g., 174 F. and 70 F.,

0.175 pounds of mist per pound of dry air is released, all at atemperature of 122.5

In a newspaper application of 2000 f.p.m., or 1200 pounds ofpaper/hr./ft. wide and a 10" Hg header vacuum, complete demisting wouldtheoretically add 18.8 pounds of water per foot of suction header or l/2% moisture per foot of header. Assuming a minimum of a 66% filteringefficiency, the feasibility of adding as high as 5% in five feet hasbeen confirmed through operation of equipment similar to that shown inthe drawing.

What is claimed is: 1. A method of applying moisture to an air perviousweb, such as uncalendered paper, comprising:

continuously supplying substantially moisture saturated air to a firstchamber by means which effects general distribution of said air withinthe first chamber;

supplying substantially moisture saturated air to a second chamber withthe second-mentioned air at a different temperature from that of the airsupplied to the first chamber for formation of a mist when mixedtherewith;

mixing the air of the second chamber with that of the first chamber byforcing it into the first chamber through a multiplicity of smallopenings to form a uniform mixture with the air of the first chamber anddirecting the resulting uniform mixture of air and the resulting mistthrough a multiplicity of small openings onto one side of the web;

subjecting a portion of the other side of the web substantiallycoextensive with said multiplicity of openings discharging onto said oneside of the web to suction to establish a path of travel of said uniformmixture of air directly through the web to collect there in the mistcarried by said air mixture.

2. Apparatus for moisturizing an air pervious web comprising:

a hollow suction box having a flat perforated Wall;

means for creating a partial vacuum in said suction box;

an air header having an outer perforated wall facing said suction boxwall and providing a multiplicity of small openings therethrough, an endwall spaced therefrom, side walls connecting said perforated wall andsaid end wall, and an interior perforated wall which extends to each ofthe side walls positioned between the outer perforated wall and the endwall to define a first chamber adjacent said outer perforated wallcontiguous with perforations therethrough, and a second chamber at anopposite side of said interior wall communicating with the first chamberthrough a multiplicity of small openings through said interior wall;

said perforated wall of the suction box having a perforated area spacedin opposed generally parallel coextensive relation with an area definingsaid multiplicity of openings of said outer perforated wall for passageof said web therebetween;

means for introducing a first stream of substantially saturated air intosaid first chamber; means for introducing a second stream ofsubstantially saturated air at a substantially different temperaturethan that of the first stream into said second chamber;

said openings of said inerior perforated wall and said means forintroducing said first stream being relatively arranged to obtainuniform mixing of said two air streams in said first chamber adjacentsaid outer perforated wall; and

means for conveying said Web between said perforated wall of the suctionbox and said outer perforated wall of the air header.

3. The apparatus of claim 2 wherein:

said conveying means is a continuous felt for supporting said web; andsaid perforated wall of the suction box and the outer perforated wall ofthe header are spaced for passage of said Web and said felt there-2,718,065 9/ 1955 Conti 3423 between. 2,370,811 3/1945 Osgood 3437 X 4.The apparatus of claim 2 wherein: 2,838,982 6/ 1958 Dupasquier 162290said conveying means, suction box, and header are 3,320,676 5/1967Speers 3423 arranged to locate the suction box above the web 1,843,6562/1932 Tompkins et a1. 162207 X path and the header directly underneaththe web 0 1,279,170 9/1918 Sullivan 162-374 X path and the suction box.

S. LEON BASHORE, Primary Examiner References Cited R. v. FISHER, Assist.Examiner UNITED STATES PATENTS 10 2,627,667 2/1953 Gillis 34 23 US2,464,119 3/1949 Dawson 34-155 3423,26,155;162290 3,238,635 3/19'66Gravenstreter 3423

